For example, in the lens barrel of a monitor camera, a movable lens for focus adjustment is arranged movable in the optical-axis direction. By changing the position of the movable lens on motor power, focus adjustment is to be performed.
As for the lens feed mechanism arranged to move a movable lens in the optical-axis direction on motor power in order to perform a focus adjustment or so, there is generally included a structure as described in JP-A-11-264925. In JP-A-11-264925, the movable lens is held in a lens frame. The lens frame is slidably supported over a guide rod fixed to the fixed lens barrel and extending in the optical-axis direction so that the lens frame, together with the movable lens, can be guided in the optical-axis direction along the guide rod.
Meanwhile, a motor-rotated feed screw is provided parallel with the guide rod and in the optical axis direction. The lens frame is connected to the feed screw through a connecting unit (driver in JP-A-11-264925). The connecting unit has one end connected swingably to the lens frame on the axis in the optical axis direction, and the other end formed with a rack mechanism engaging on the feed screw in a manner clamping the feed screw.
When the feed screw is rotated by the motor, the connecting unit is moved forward and backward in the optical-axis direction by the rack mechanism. In conjunction therewith, the lens frame connected to the connecting unit and the movable lens held in the lens frame are moved forward and backward in the optical-axis direction.
However, in the background art, the connecting unit is formed in one body as in JP-A-11-264925. Consequently, there is a need to accurately arrange the guide rod to guide the lens frame in the optical-axis direction as well as the feed screw to be rotated by the motor. When the feed screw is arranged inaccurately and hence the parallelism is low between the guide rod and the feed screw, the lens frame is acted with a force in a direction deviated from the guide rod. Consequently, the movable lens held in the lens frame has its optical axis deviating from the proper optical axis of the optical system overall, possibly incurring the lowering of optical characteristic. Besides, an increase of load between the lens frame and the guide rod occurs, possibly causing a malfunction or giving an adverse effect upon durability.